Capture gamma-ray Assessment in Nuclear Energy (C-GANE)

核能是通过两个原理获得的：1）裂变，通过诱导重原子分裂成较轻的元素来释放能量; 2）聚变，通过将轻原子融合在一起形成较重的原子来释放能量。裂变技术已经成熟，并在世界大部分地区得到应用;聚变是重要的研究和投资的主题，因为它有潜力产生低碳、不间断的能量生产，而不产生裂变中产生的高活性放射性废物。当裂变反应堆中使用的燃料达到其使用寿命的终点时，它被认为是耗尽的，并被储存或溶解和分离（后者被称为再处理）。人们普遍期望，来自裂变反应堆的未经后处理的乏燃料将以完整的燃料组件形式进行处置。然而，到目前为止，在英国，大部分都储存在水下，以确保它得到满意的冷却，并屏蔽来自它的辐射，这导致一些组件内部有水。同样，如果燃料材料以无序形式存在，例如，与来自加工操作和事故的杂项废物（称为含燃料材料- FCM）相关，则通常将其储存在筒仓中，并且再次需要评估存在的水的丰度。在永久处置乏燃料和FCM之前，必须了解乏燃料和FCM中水丰度的情况（例如在地下储存库中）因为水对燃料的稳定性构成重大影响以防止意外的核反应，并且这可能影响它如何被存储以及关于它被存储在其中的存储库的设计的安全情况。一个相关的最近的例子，也许是最近最引人注目的例子，涉及切尔诺贝利的FCM。这在2021年得到了媒体的广泛报道，当时观察到它发出的中子辐射水平正在增加。这些碎片被一个新的覆盖物所覆盖，以保护其免受自然元素的影响，人们怀疑这导致了材料中裂变率的上升。在含有燃料的材料中，中子主要来自铀-235的裂变，令人关切的是，碎片中含水量的下降会导致这种情况增加，最终可能导致不受控制的能量释放。然而，发射也可能增加，这是由于减少了水对中子的屏蔽和吸收，使更多的中子能够出去，或者由于α粒子的中子发射反应增加，或者由于使用的中子探测器在更高的能量下更有效地响应，没有一个比铀235的诱发裂变升级更严重的影响。与测量中子通量不同，这是切尔诺贝利FCM关注的问题，通过探测当中子被周围材料中的同位素捕获时所发射的伽马射线，可能会对这个复杂的问题有更深入的了解。这样做的优点是，伽马射线具有产生它们的同位素所特有的能量，并且它们相对容易测量：这是本提案的重点。例如，氢发射具有2.223 MeV的容易识别的能量的伽马射线，这可能是水含量变化的特征，并且可能与中子环境的变化分离。有趣的是，除了中子发射之外，测量聚变功率的少数方法之一也是研究这些发射，例如考虑氘氚反应的16.7 MeV发射。在这个项目中，我们打算把这些机会结合在一起，以确定裂变和聚变能量是否可能受益于高能俘获伽马光谱。

Nuclear energy is made available via two principles: 1) fission, in which energy is released by inducing heavy atoms to split into lighter elements, and 2) fusion, where energy is released by fusing light atoms together forming heavier ones. Fission is mature and is used throughout much of the world; fusion is the subject of significant research and investment, due to its potential to yield low-carbon, uninterrupted energy production without the yield of high-active radioactive waste produced in fission.When the fuel used in fission reactors reaches the end of its useful life it is deemed spent, and is either stored or dissolved and separated (the latter known as being reprocessed). The widespread expectation is that spent fuel from fission reactors that is not reprocessed will be disposed of in the form of intact fuel assemblies. However, thus far in the UK much of it has been stored under water to ensure that it is cooled satisfactorily and that the radiation from it is shielded, and this has resulted in some of the assemblies having water inside them. Similarly, where fuel material exists in disordered form associated with, for example, miscellaneous wastes from processing operations and accidents (known as fuel containing materials - FCM), often it has been stored in silos and again the abundance of water present needs to be assessed. It is important to understand the extent of the situation concerning water abundance in spent fuel and FCM prior to it being disposed of permanently (for example in an underground repository) because the water constitutes a significant influence on the stability of the fuel against an inadvertent nuclear reaction, and this could influence how it is stored and the safety case concerning the design of the repository it is stored in.A relevant recent example, and perhaps the highest-profile illustration of late, concerns the FCM at Chernobyl. This received widespread media coverage in 2021 when it was observed that the level of neutron radiation emitted by it was increasing. The debris in question had been shrouded by a new cover erected over the site to protect it from the elements and the suspicion arose that this was causing the fission rate in the material to escalate. Neutrons arise in materials containing fuel predominantly from fission in uranium-235, with the concern being that a fall in the water content in the debris was causing this to increase with the ultimate potential for uncontrolled energy release. However, the emission might also increase due to reduced shielding and absorption of neutrons by a reducing quantity of water, enabling more neutrons to get out, or by an increase in neutron-emitting reactions by alpha particles or due to the neutron detectors being used responding more efficiently at higher energies, none of which have implications as serious as an escalation in induced fission on uranium-235.Rather than measuring the neutron flux, as was the source of concern for the FCM at Chernobyl, greater insight might be gained concerning this complex problem by detecting the gamma rays that are emitted when neutrons are captured by isotopes in the surrounding materials. This has the advantage that the gamma rays have energies that are characteristic of the isotope producing them and that they are measured relatively easily: this is the focus of this proposal. For example, hydrogen emits gamma rays with an easily-identifiable energy of 2.223 MeV which could be characteristic of changes in water content and which might be separable from changes in the neutron environment. Interestingly, one of the few ways to measure fusion power aside from the neutron emission is also to study these emissions, by for example considering the 16.7 MeV emission from the deuterium-tritium reaction. In this project, we intend to bring together these opportunities to determine whether fission and fusion energy might benefit from high-energy capture gamma spectroscopy.